Back here at home, we turn to an American icon. Baseball great Lou Gehrig. On this date 75 years ago, he delivers the most important speech in sports history. Reporter: The sun was hot at Yankee stadium that July 4th, and the man was so sick. But in his opening few words, he was not going to let that show. Bad break. Reporter: Yes, they had been Reading about it. Number 4 was out of the game for good. But even so, his very next line was so perfect. So perfectly Gehrig. Today, I consider myself the luckiest man on the face of the Earth. Reporter: Baseball's most famous 13 words. Because it seemed he absolutely meant it. Less known is the rest of what Gehrig said that July 4th. Only a few of his lined exist on camera. But we now know, he talked about how lucky he was to have had the teammates he did, and the wife he married, and the parents he had been given. And today, in a major league baseball video, fellow first basemen recite the speech, wearing this patch on their sleeves, to raise awareness for that disease now named for him. It's true, many of us know the 13 words from the movie "Pride of the yankees," which diverged a lot from the real speech, turned its famous opening into its closing line instead. The luckiest man on the face of the Earth. Reporter: How did Gehrig actually close? Perfectly. I have a lot to live for. Thank you. John donvan, ABC news, Washington. What a class act.

This transcript has been automatically generated and may not be 100% accurate.

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